Electromagnet for circuit breakers and the like



Feb. 20, 1934. R. c. DICKINSON ELECTROMAGNET FOR CIRCUIT BREAKERS ANDTHE LIKE Filed Jan. 19, 1928 Fig. 3.

Fig.2.

INVENTOR Raberf C Dickinson.

AITTORNEY Patented Feb. 20, 1934 ELECTROMAGNET FOR CIRCUIT BREAKERS ANDTHE LIKE Robert C. Dickinson, Wilkinsburg, Pa., assignor to WestinghouseElectric & Manufacturing Company, a corporation of PennsylvaniaApplication January 19, 1928. Serial No. 247,829

Claims.

My invention relates to circuit interrupters, and more particularly toelectro-magnets for maintaining them in their closed positions.

One object of my invention is to provide a 5 circuit interrupter with anelectro-magnet that shall operate to open the circuit very quickly afterthe occurrence of an overload or other abnormal circuit condition.

Another object is to provide an electromagnet responsive to a maximumvalue of either alternating current or direct current.

Another object of my invention is to provide a circuit interrupter withan electro-magnet that shall be adapted to open the circuit upon theoccurrence of an overload on either an alternating-current or adirect-current circuit.

A further object of my invention is to provide a circuit interrupterwith an electro-magnet that shall be adapted to permit it to move to itsopen position with great rapidity when actuated by an increase ofcurrent in the circuit.

Heretoiore, certain circuit interrupters intended for use ondirect-current circuits have been provided with electro-magnets having aseparately excited winding for holding the circuit-interrupter in closedposition and which are operated to release the circuit interrupter uponthe occurrence of an overload in the circuit, by reason of beingprovided with a second winding energized to oppose the first-mentionedwinding and neutralize its holding efiect. By properly proportioning thetwo coils, such balance may be obtained that an armature may be releasedwhen the current in the neutralizing winding has attained a certainvalue. Attempts to apply this principle to alternating currents havebeen more or less unsuccessful for the reason that it was necessary toemploy either rectifiers or electromagnets having cumbersome magneticcircuits to produce release of the armature member.

In practicing my invention, I am able to construct a holdingelectro-magnet that employs no polarized magnets and that, accordingly,may be operated on either an alternating or a directcurrent circuit toopen the circuit when an increase of current occurs in the circuit.

Referring to the drawing:

Figure 1 is a diagrammatic view of a particular embodiment of myinvention in which the holding electro-magnet is energized from adirectcurrent source.

Fig. 2 is a sectional view of a particular embodiment of my core membershowing the parallel path traversed by the line-current circuit in thedevice shown in Fig. l.

Fig. 3 is a diagrammatic view showing the flux distribution in the coremember and the armature when normal current is flowing in the twocircuits.

My invention comprises, in general, a circuit 50 interrupter 1 that isheld in closed position by latch The latch 2 is controlled by anarmature 3 which engages the magnetic core 4 of a holding electro-maghet5.

The core 4 is or" E shape, that is to say, it comprises a central leg 6and two end legs 7 and 8. A winding 9 is located about the lower portionof the central leg 6 and may be energized any constant source ofpotential, such as the battery 11. The upper half of the central 7 leg 6is provided with arms 12 and 13 that provide a shunt path for the fluxinduced in the core 4 by the line current, in a manner that will be morefully explained hereinafter. Channels 14 and 15 are thus provided in theupper part of the core 4 through which the bars 17 and 18 extend. .Thebars 1*. and 18 are traversed by the main-circuit current which thusdivides near the core 4 into these two paths, passing between theoutside legs and the central leg of the core 4. In Fig. l, the bars 17and 18 are shown connected to one side of a current transformer 19,although they may beconnected to a direct-current source 21, in themanner indicated in Fig. 2.

The armature 3 is biased to open position by a spring 22 and ispivotally supported upon a lever 23 that is supported near its center ona fixed pivot 24. The other end of the lever 23 contains a latchingmeans 25 for holding the circuit interrupter l in closed position.

The circuit interrupter 1 comprises an operating arm 26 that is biasedby the spring 27 to open position against stop member 28 and ispivotally supported on a fixed pivot 29. A bridging member 31 isconnected to the upper end of arm 26 and is employed to bridge contactmembers 32 and 33 to complete a circuit in the main line 34.

A spring 35 is connected between the operating member 26 and the latch 2to bias the latter into engagement with t. e latch 25. Stop member 36 isprovided on the operating member 26 to prevent the member 2 from beingdrawn too far downward, thereby ensuring its engagement with the latch25 upon the closing of the circuit interrupter 1.

Referring to Fig. 3, the circles enclosing crosses indicate, by afamiliar convention, that the current in the parallel circuits 1'7 and18 is flowing in the same direction. This current may be supplied fromeither an alternating-current or a di-' 110 rect-current source. Anormal holding flux, indicated by the arrows 37, is produced in themagnetic circuit by the winding 9 that is energized by the battery 11 orany other source of invariable energy. The strength of the coil 9 is sochosen that the flux 37, induced thereby in the magnetic circuit formedby the armature 3 and the core 4, is sufiicient to produce saturation inthe iron of the armature 3. The current supplied by the line to thepaths 17 and 13 produces fipxes in the same direction in the armature 3,as indicated by the arrows 38.

The arms 12 and 13 provide a magnetic circuit encircling the bars 17 and18, thereby increasing the magnitude of the fluxes 38.

It will thus be seen that, if the current in the paths 1'7 and 18 issufficiently increased, the fiux produced by the current in bar 18 will,as shown in Fig. 3, be in the opposite direction to the flux 37 normallypresent therein and will reduce the net flux in the adjacent end of thearmature 3.

On the other hand, the flux 38 induced by the current in bar 17 has thesame direction as the flux 37 and will tend to increase the number oflines of force on the other end of the armature 3. Because of thesaturated condition of the armature 3, however, little or no increase inthe holding force on the right hand end of armature 3 will result. Thesum of the next fluxes through the two ends of armature 3 is, therefore,decreased and, if the current in the parallel conductors 17 and 18reaches a certain value, the spring 22, shown in Fig. 1, will operate topull the armature 3 to its open position.

The same result will be obtained if an overload occurs while thedirection of the current in the circuit is reversed. The flux about thepath 18 will then assist, and that about the path 17 will oppose thenormal flux 37. The only change produced by reversal of current is,therefore, that the other end or" the armature 3 is the one in which theflux decreases. The effect on releasing armature 3 will be no diiferentfrom that just described.

As the armature 3 moves to its open position, the latch 25 moves fromunder the trigger 2, releasing the operating arm 26 of circuitinterrupter l. The arm 26 is quickly drawn over against the stop member28 by the energy stored in the spring 27. This movement of the arm 26moves the bridging member 31 away from the contact members 32 and 33 andthus opens the circuit of the main line 34.

In closing the circuit interrupter, the armature 3 is first moved to itscircuit-closing position, that is to say, into engagement with the coremember 4. Member 4 being energized by the winding 9, holds the armature3 in that position. The operating arm 26 of the circuit interrupter 1 isnext moved forward until the bridging member 31 engages the contactmembers 32 and 33, at which time the trigger 2 engages latch 25 and isdrawn downwardly into engaged position by the spring 35. Thecircuit-interrupter is thus latched in closed position.

This method of employing a latch to operate the bridging member is usedonly as an illustration, and it will readily be seen that otherconnections may be made without departing from the scope of theinvention. As an example, the armature 3 could be shown connecteddirectly to the bridging member 31, and the latch 25 would be omitted.

It will thus be seen that I have provided a hold ing magnet for acircuit interrupter that is adapted to open the circuit interrupter whenthe holding electro-magnet is excited from either an alternating or adirect-current source. My invention is further novel in that nopolarized electromagnets are employed in its operation, and the releaseof the armature is obtained by the employment of current coils thatproduce uni-directional fluxes in the magnetic circuit.

It is' to be understood that such changes in the form, arrangement andconnection of component parts of my invention may be made as shall fallwithin the scope of the appended claims.

I claim as my invention:

1. An electromagnet comprising a core member and anarmature, a normalmagnetizing winding saturating the core member to retain the armature inclosed position, a conductor that divides on passing through the coremember to form parallel current paths one of which produces amagnetizing force that assists, the other a magnetiz- .ing force thatopposes, the normal magnetic flux in the armature in such manner that apredetermined increase ofcurrent in said conductor releases the armaturefrom engagement withthe core member.

2. An electromagnet comprising a core member and an armature, meansnormally exciting the core member to retain the armature thereagainst inengagement therewith against the pull of a. bias means, the saidexciting means being of such strength that the armature is highlysaturated, a pair, of conductors associated with the core member inparallel relation to produce fluxes in those parts of the core memberand armature associated with each conductor, in addition to the fluxproduced by the first said exciting means, and so disposed as to reducethe flux on one end of the armature but not to increase the flux in theother end because of its saturated condition, thereby producing therelease of the armature on a predeterminedincrease in current in saidconductor.

3. An electromagnet for circuit interrupter-s and the like comprising anE-shaped core and an armature biased away from the core, a. coil aboutthe middle leg of the E-shaped core adapted to supply sufficientmagnetizing force to highly saturate the armature, and'a circuit thatcomprises parallel conductors on each side of the middle leg of saidE-shaped core, said conductors being so arranged relative to each otherthat one opposes and the other assists the magnetizing force of saidcoil, whereby, upon increase beyond a predetermined value of current,said armature will be released.

4. An electromagnet responsive to either direct or alternating currentand comprising core means, armature means, means biasing the armaturemeans away from the, core means, means for normally exciting the coremeans to draw the armature means thereto against the force of thebiasing means, the exciting means being of sumcient strength tosubstantially saturate the core means, and current conducting meansarranged to produce two fluxes, one of which reduces a part of the fluxproduced by the excitingmeansand the other of which tends to increaseanother part of said flux but is substantially inefiective because ofthe saturated condition of the core means, whereby, when the currentflowing through the conducting means exceeds a predetermined value,regardless of direction offiow, thetotal effective flux will be reducedand permit the biasing means to move the armature means away from thecore means.

fluxes, one of which reduces a part of the flux produced by the excitingmeans and the other of which tends to increase another part of said fluxbut is substantially ineffective, because of the saturated condition ofthe core means, whereby, when the current flowing through said circuitexceeds a predetermined value, the total efiective flux will be reducedand permit the biasing means to move the armature means away from thecore means.

ROBERT C. DICKINSON.

